Construction of shuttle vectors derived fromAcetobacter xylinum for cellulose-producing bacteriumAcetobacter xylinum

Summary Shuttle vector pUF106 was constructed by ligation ofAcetobacter xylinum plasmid pFF6 toEscherichia coli plasmid pUC18. It had unique restriction sites suitable for insertion of a foreign DNA fragment and conferred ampicillin resistance to a host. pUF106 transformed cellulose-producingA. xylinum ATCC10245 as well asE. coli JM109.     

Molecular cloning of cDNA for the import precursor of human subunit B of H(+)-ATP synthase in mitochondria.

The nucleotide sequence of the import precursor of subunit b of human H(+)-ATP synthase has been determined from a recombinant cDNA clone isolated by screening a human kidney cDNA library with a cDNA for rat subunit b as a probe. The sequence was composed of 1,134 nucleotides including a coding region for the import precursor of subunit b and noncoding regions on the 5'- and 3'-sides. The import precursor of subunit b and its mature polypeptide deduced from the open reading frame were found to consist of 256 and 214 amino acid residues with molecular weights of 28,893 and 24,610, respectively. The presequence of 42 amino acids could be the import signal peptide for directing the protein into the mitochondrial matrix.     

Budding-specific lectin induced in epithelial cells is an extracellular matrix component for stem cell aggregation in tunicates.

We have examined immunocytochemically the expression, localization and in vivo function of a calcium-dependent and galactose-binding 14 x 10(3) Mr lectin purified from the budding tunicate, Polyandrocarpa misakiensis. Lectin granules first appeared in the inner epithelium of a double-walled bud vesicle. Soon after the bud entered the developmental phase, the granules were secreted into the mesenchymal space, where the lectin-positive extracellular matrix (ECM) developed. The lectin was also produced and secreted by granular leucocytes during budding. Hemoblasts, pluripotent stem cells in the blood, were often found in association with the ECM and they aggregated with epithelial cells to form organ rudiments. The lectin showed a high binding affinity for hemoblast precursors. The blockage of epithelial transformation of stem cells by galactose in in vivo bioassy was ineffective in the presence of the lectin. Polyclonal anti-lectin antibody prevented the hemoblasts spreading on the ECM and moving toward the epithelium, but it did not block the cell-cell adhesion of hemoblasts. By three days of bud development, lectin granules and ECM have almost disappeared from the developing bud together with a cessation of hemoblast aggregation. These results show that Polyandrocarpa lectin is a component of the ECM induced specifically in budding and suggest strongly that it plays a role in bud morphogenesis by directing the migration of pluripotent stem cells to the epithelium.     

Comparison of the intestinal bacteria in specific pathogen free mice from different breeders

Specific pathogen free BALB/c mice from 3 commercial laboratory animal breeders in Japan were compared on the composition of caecal flora revealed by selective and nonselective cultivation as well as direct microscopical observation on smears, and relative caecal weight. Large differences were detected in viable counts of total bacteria and almost all bacterial groups, while direct microscopical counts which consisted mainly of fusiform bacteria were almost equal, resulting in diverse recovery rates among 3 breeders. Eubacterium and spiral shaped organisms were not detected from all breeders. There also existed variations within breeders, especially those in the number of Enterobacteriaceae. Relative caecal weight also differed among breeders, suggesting the participation of variety of caecal bacteria in determining this parameter. As these variations in bacteriological status of animals can influence experimental results, standardization of intestinal microbial flora is required.     

Characteristics of a circadian pacemaker in the suprachiasmatic nucleus

Summary The nature of the circadian rhythms of the SCN in a hypothalamic island was examined in male rats by recording multiple unit activity from the SCN for longer durations. Successful continuous recording lasted up to 35 days. Neural activity of the SCN inside the island showed free-running rhythms whose periods were slightly longer than 24 h (Figs. 2, 3, Table 1). When the retino-hypothalamic pathway was spared, re-entrainment to a displaced light and dark cycle was attained following a transition period of a few days (Fig. 4). Phases of the rhythms shifted in a phase-dependent manner in response to single light pulses interrupting constant darkness (Fig. 5 and Fig. 6). These results suggest an endogenous nature of the circadian rhythm of the SCN within the hypothalamic island. Thus, neurons or neuronal networks in the SCN may have not only an inherent ability to generate a circadian rhythm, but also an intricate machinery to regulate its phase. Simultaneous recordings from the left and right SCN showed a slight but visible discrepancy in their phases between the two rhythms in 3 out of 12 cases (Fig. 7).Abbreviations LL constant light - LD light-dark - DD constant darkness - SCN Suprachiasmatic nucleus     

Biosynthesis of Auxin-Induced Ethylene. Effects of Indole-3-Acetic Acid, Benzyladenine and Abscisic Acid on Endogenous Levels of 1-Aminocyclopropane-l-Carboxylic Acid (ACC) and ACC Synthase

Auxin-induced ethylene biosynthesis and its regulatory stepsin etiolated mung bean hypocotyl segments were examined. Theendogenous content of 1-aminocyclopropane- 1-carboxylic acid(ACC), an immediate precursor of ethylene, increased correspondingto the rate of ethylene production. Benzyladenine (BA), whichis a synergistic stimulator of auxin-induced ethylene production,increased the ACC content parallel to the rate of ethylene productionin the presence of IAA, but failed to increase the ACC contentin the absence of IAA while ethylene production was significantlystimulated by BA. Abscisic acid (ABA) inhibited the formationof ACC. The ACC synthase activity in the tissue was increasedby IAA, and the increase was further promoted by the presenceof BA. Cycloheximide severely inhibited the development of auxin-inducedACC synthase. The enzymatic properties of mung bean ACC synthasewere similar to those of the tomato fruit enzyme. Aminoethoxyvinylglycine(AVG) and aminooxyacetic acid, which inhibit the ACC synthasereaction, stimulated the development of ACC synthase. The regulatorymechanisms of the growth regulators are discussed in relationto ACC formation. (Received December 3, 1980; Accepted January 22, 1981)     

Cytological studies on the mosaic silkworms induced by low temperature treatment

Mosaic silkworms were induced when the hybrid eggs of two strains with different egg color and larval markings were exposed to low temperature. Cytological studies were conducted to find out the relation between mosaic larval pattern and ploidy in reproductive cells along with demonstration of chromosomes in the mosaic embryos. — Mosaic eggs eith the characters of both the father and the hybrid were two types, one with large serosa nuclei (LN-mosaic) and the other with small serosa nuclei (SN-mosaic). The cytological studies demonstrated that LN-mosaic individuals were 2n/4n, while SN-mosaic ones were n/2n. In both types of silkworms, cell ploidy level in nuclei of synkaryon origin was two times that of androgenic ones. — From the results obtained in the present studies as well as in the previous studies, a possible mechanism of induction of mosaicism in silkworms by cold shock is contemplated.     

Ceramide metabolism in brain

Summary Ceramide is the fundamental structure and key intermediate of all sphingolipids. Biosynthesis and catabolism of brain ceramide, especially their relationship to the metabolism of more complex sphingolipids in brain, are reviewed. Human genetic diseases which involve altered ceramide metabolism are also discussed.     

The fine structure of ventral prostatic secretory epithelial cells in older rats

Summary The ventral prostatic secretory epithelial cells in older rats were studied by light and electron microscopy. The cells vary in height in different parts of the same organ, and ultrastructurally they show the presence of a developed secretory apparatus such as well-developed Golgi body and abundant rough endoplasmic reticulum. They also show signs of a depressed secretory activity, involving occasional emiocytosis of apical secretory vacuoles and a paucity of condensing vacuoles in the Golgi region and above it. Further, they are characterized by the frequent occurrence of supra and paranuclear pleomorphic lysosomes.     

Suppression and stimulation of DNA synthesis by ADP-ribosylation of nuclear proteins from adult hen and chick embryo liver.

The stimulation of DNA synthesis by ADP-ribosylation of nuclear proteins was observed in chick embryo liver nuclei. In contrast, a significant decrease in template activity was detected in hen liver nuclei treated with NAD. When a 0.35 M NaCl extract from embryo, but not adult, liver nuclei was treated with NAD and then combined with either adult or embryo liver nuclear residue, the ability to activate the template was greatly enhanced. These results indicate that in the chick embryo liver, the ADP-ribosylation of the nuclei plays an important role as a regulator of DNA synthesis.